Format of REAL/32 XIOS header structure:
Offset	Size	Description	)
 00h  3 BYTEs	XIOS initialization entry point
 03h  3 BYTEs	XIOS service entry point
 06h	WORD	segment address of system data
 08h	DWORD	address of supervisor entry point
 0Ch	BYTE	set tick flag
 0Dh	BYTE	ticks per second
 0Eh	BYTE	global Door Open interrupt flag
 0Fh	BYTE	number of Auxiliary Control Blocks
 10h	BYTE	number of physical consoles
 11h	BYTE	number of virtual consoles
 12h	BYTE	number of logical consoles
 13h	BYTE	number of list control blocks
 14h	WORD	offset of CCB table
 16h	WORD	offset of LCB table
 18h 16 WORDs	offsets into DPH for drives A-P
 38h	WORD	buffer size in paragraphs
 3Ah	WORD	offset of ACB table
 3Ch	WORD	used by OEM
 3Eh	WORD	offset of CCB pointer array
 40h	WORD	offset of LCB pointer array
 42h	WORD	offset of ACB pointer array
 44h	BYTE	'first' flag
 45h	BYTE	unused
 46h	WORD	offset of print device support table
 48h	WORD	offset of aux device support table
 4Ah	WORD	XIOS extra segment
 4Ch	WORD	segment of save end address for debug
 4Eh	WORD	segment of save start address for debug
 50h	BYTE	number of main virtual console
 51h	WORD	segment of XIOS code
SeeAlso: #04048